This disclosure relates generally to a coupling member and, more particularly, to a Hirth coupling member joining static turbomachine components having dissimilar temperatures, which are also required to have high stiffness, and particularly those with limited packaging space.
Turbomachines include many components. During operation of the turbomachine, some of the components reach very high temperatures. Other components must maintain at lower temperatures. A bearing compartment, for example, must be maintained at or below 400° F. (204° C.) to avoid lubricant contained by the bearing compartment degrading or reaching its flashpoint. Other components in the turbomachine reach temperatures up to 2100° F. (1199° C.) or more.
Joining lower-temperature components, such as the bearing compartment, to other components that reach higher temperatures is often difficult. The higher-temperature components grow more than the lower-temperature components, which strains one or both of the components. The strain is particularly prevalent in turboshaft and small-core commercial gas turbine engines as these engines provide very little space to accommodate a high thermal gradient between components.
Coupling strategies for components must accommodate the strain resulting from the thermal gradients described above. Introducing flexibility to the coupling strategy would help, but turbomachines typically require highly rigid connections, especially between the bearing compartment and the outer structure of the engine to control lateral deflection and critical speeds of the rotating components. The coupling must also provide very tight concentricity control between the two components to maintain engine bearing alignment and close clearances between rotating and static components. The inherent conflict between these requirements can drive significant compromise into the overall engine design.